Updated version to 2.1.2 and samples

Updated the model-core plugins.sbt and demos (both java and scala
versions) plugins.sbt to scala version 2.1.2.
Additionally, modified the java and scala demos conf/securesocial.conf
files, in order to support the following configuration files

onStartSignUpGoTo=/login
onSignUpGoTo=/login
onStartResetPasswordGoTo=/login
onResetPasswordGoTo=/login

This allows users to know how to make custom login
flows without having to dive into the source code.

And also the following ones introduce in the precious commit:

providerController=securesocial.controllers.ReverseProviderController
loginController=securesocial.controllers.ReverseLoginPage
registrationController=securesocial.controllers.ReverseRegistration
passwordChangeController=securesocial.controllers.ReversePasswordChange
assetsController=controllers.ReverseAssets

That allows for custom creation of controllers in order to create
complex authentication flows.

Finally, fixed mixed spaces and tabs indentations in those files.